Cadillac has done well with GM’s Sigma platform. The rear-drive architecture has served under two generationsof CTS, the passable if somewhat mundane STS, and Caddy’s first crossover, the original SRX. That said, the bones were altered—some feel compromised—to accommodate the now-defunct hulk known as the Northstar V-8, and ended up being far from cost-effective. Also, unlike the majority of GM’s platforms, Sigma has a relatively limited size bandwidth, as demonstrated by the dimensional similarities between the CTS and STS, and even the STS’s long-wheelbase sibling, the Chinese-built SLS. With the STS dead, the SRX now shifted to front-wheel-drive underpinnings, and the next-generation CTS migrating to the General’s new, highly versatile, and lighter Alpha platform, Sigma’s days are numbered.

Cue “The Imperial March”

Although the Alpha platform appears to be one of the best rear-wheel-drive component sets in the business, GM still recognized a need for an additional, larger RWD platform for the oft-rumored apocryphal “Cadillac flagship,” among other vehicles. Early thoughts for the kingly ride ranged from an eye-wateringly expensive model on a bespoke architecture (think Rolls-Royce Phantom) to a kind of monster sedan spun from the original Zeta platform (think widened Chevrolet Caprice cop car with a longer wheelbase). It seems the smart guys in the room prevailed and a middle-ground solution was devised: the Omega platform.

As platforms go, the Omega is as “all-new” as anybody is doing these days. Sure, most of the drivetrain equipment will be shared with other GM rear-drive cars and the rear-suspension geometry is intellectually related to that of Alpha, but there is no real commonality with the smaller platform beyond the way it all goes together in a plant. While Alpha is good for cars and crossovers ranging in size from something slightly smaller than the current BMW 3-series to a vehicle a bit larger than a 5-series, Omega moves up from there. At the bottom of its scale you could build a wider 5-series, while its upper bounds are said to be a vehicle measuring around 207 inches in length bumper-to-bumper (a couple of inches longer than a long-wheelbase 7).

The first product off the platform is a lineup-crowning successor to the still-to-be-introduced Epsilon-derived XTS. (This is not the flagship-y flagship.) Yep, a proper rear-drive sedan will supplant—if not completely replace—the XTS at the top of Cadillac’s offerings in about two and a half years; it will have the fast roofline currently applied to everything from the latest Ford Fusion to the Audi A7. In not-surprising news, the General’s 3.6-liter “high-feature” DOHC V-6—making around 310 hp—is expected to be the standard engine. A low-pressure, torque-biased take on the twin-turbo version of that engine—currently being prepped for the ATS-V, as we reported last May—could be plugged in as an alternative to the currently planned optional powerplant, the new-gen Tonawanda, New York–built “mystery” V-8. Regardless of powerplant, drive will be transmitted to the wheels through an all-new eight-speed automatic that also will find its way into the CTS, the ATS, and some GM trucks. While the default powertrain will be rear-drive, all-wheel drive will be offered to make sure the Omegas can be sold year-round in the Snow Belt, Rockies, and Pacific Northwest. With GM’s longitudinal dual-mode hybrid technology presently tied to a long-in-the-tooth four-speed automatic, there are rumblings the system will be reconfigured with the upcoming eight-speed. Although it is unclear if a hybrid is planned for the first Omega product, the platform has been designed to accommodate the batteries and ancillary bits of GM’s gas-electric systems.

The Void is Calling: Let’s Do the Flagship (Talk) Again

Of course, Omega won’t be used for a single model. When laying out the platform, the company designed it so that it could serve as the basis for a properly huge, properly sybaritic Cadillac flagship. This favorite of automotive journalists and bloggers has been rumored for years; its origins can be traced to the striking yet somehow comical Cadillac Sixteen concept. The division telegraphed its continued interest in building an über-Caddy last summer when it rolled out the Cadillac Ciel four-door convertible at the Pebble Beach Concours d’Elegance. (Here’s what the Ciel would look like as a sedan; pretty cool, right?) Whether the flagship ends up being a four-door sedan, a big two- or four-door convertible, or a large, Mercedes CL–fighting coupe, it’ll be underpinned by Omega. Aside from the issue of the program’s approval, the biggest conundrum around the flagship program is the question of powerplant: Do any of GM’s current mills have the power, refinement, and prestige to do the job, or will the company, say, have to restart development of a twelve- or—gasp!—sixteen­-cylinder?

Mo’ ’Mega

Beyond the identified XLS-augmenting sedan, a number of additional Omega derivatives are being discussed. While it’s no surprise that a crossover is at the top of the list, at first glance this appears to conflict with Cadillac’s upcoming Lambda crossover. The Lambda-based Cadillac is supposed to complement the Escalade, which is slated to become more of a halo vehicle. And while current Lambda offerings (Chevrolet Traverse, GMC Acadia, and Buick Enclave) are essentially as long as a Tahoe/Yukon/Escalade, they can in no way be considered a viable alternative to the Suburban-based Escalade EXT. Omega could be used to create a near-Suburban-sized high-end Cadillac crossover. This would be an offering with no counterpart in the luxury arena. Farther down the Omega product list is a coupe that would effectively revive the Eldorado—if not in name, certainly in product position. A long-wheelbase version of the launch sedan is all but a certainty for the back-seat-happy Chinese market, and would make sense for the U.S. if Cadillac decides to position that car against the S-class/7-series/A8 trio of Teutonic sedans.

From a manufacturing standpoint, as mentioned, the aim has been to make Omega completely common from a processing standpoint with the Alpha platform. As a result, we wouldn’t be surprised to see Omega vehicles going down the line alongside the ATS and next-generation CTS at General Motors’ Lansing Grand River assembly plant.

Looking at GM’s current brands and the fact that their rear-drive needs can be serviced by the Zeta II platform, the potential for something other than a Cadillac coming off Omega is highly unlikely. In that respect, Omega is the true successor to the Sigma architecture in that it will be a Caddy exclusive.